This study, which was drawn from a larger published work, examined language proficiency and literacy skills predictive of learning content and function words via the commonly used practice of flashcard word reading, which tests word knowledge in isolation. The current study also investigated differences in word learning performance between students of different language backgrounds (native and nonnative English speakers), and between students at the same grade level but in different alphabetic phases of word reading development. Kindergarten students (n = 81) practiced learning to read content and function words on flashcards. Analyses examined the extent to which students' baseline English language skills, phonemic awareness, spelling knowledge, and/or word reading predicted performance on the word learning task. Results of linear regressions demonstrated that language skills accounted for a significant amount of unique variance in reading function words in isolation, but this was not the case for reading content words in isolation. Further, results indicated that baseline alphabetic phase, and not language background, moderated the relationship between language skills and word learning, such that language skills predicted function word learning only for full alphabetic readers and not partial alphabetic readers. Results are discussed in terms of implications for the teaching of function words as dependent on children's relative phase of literacy development rather than their language backgrounds.